Problem 33 - Chemistry in 30 days

Question

Which of the following is the anhydride of perchloric acid? (a) \(\mathrm{ClO}_{2}\) (b) \(\mathrm{ClO}_{2}\) (c) \(\mathrm{Cl}_{2} \mathrm{O}_{6}\) (d) \(\mathrm{Cl}_{2} \mathrm{O}_{7}\)

Step-by-Step Solution

Answer

The anhydride of perchloric acid is \(Cl_2O_7\).

Step 1: Understand Anhydride Formation

An anhydride is a compound that forms an acid when combined with water. In this context, the anhydride of an acid is a compound that, when reacted with water, regenerates the acid.

Step 2: Recall the Formula of Perchloric Acid

Perchloric acid is \ \( HClO_4 \). We need to find a compound that, when reacted with water, gives \( HClO_4 \).

Step 3: Analyze Each Option

Evaluate which option, when combined with water, can form perchloric acid. Consider the stoichiometry and probable reactions involved.

Step 4: Evaluate Option (d) \(Cl_2O_7\)

Combine \( Cl_2O_7 \) with water: When \( Cl_2O_7 \) reacts with water, it forms:\[ Cl_2O_7 + H_2O \rightarrow 2 HClO_4 \]This suggests that \( Cl_2O_7 \) is the anhydride of perchloric acid.

Key Concepts

Perchloric Acid

Perchloric acid is a chemical compound represented by the formula \( HClO_4 \). It is a strong acid known for its extensive use in chemical laboratories and industrial processes. As an oxidizing agent, it is vital in some chemical reactions.
Its strong acidic behavior means it dissociates completely in water, releasing hydrogen ions that contribute to the solution's acidity.

• Colorless and water-soluble, making it useful for many applications.
• Always handle it with care due to its highly reactive nature.

It's key to note that perchloric acid should only be used in controlled environments with proper safety measures due to its potential hazards.

Chemical Reactions

Chemical reactions involve the transformation of substances through the breaking and forming of chemical bonds. Reactions can be simple or complex, with the latter involving multiple steps or intermediaries.
An essential part of understanding chemical reactions is grasping how molecules interact and transform into different compounds.

• Every chemical reaction follows a specific pattern, although reactions can vary widely in nature and complexity.
• Reactions can be classified into different types, such as synthesis, decomposition, single replacement, double replacement, and combustion.

In the case of perchloric acid, its formation results from the combination of its anhydride \( Cl_2O_7 \) with water, which is a type of synthesis reaction.

Anhydride Formation

Anhydrides are a class of compounds that play a significant role in forming various acids. The term "anhydride" means "without water," referencing how such compounds can be formed by removing water from an acid.
The concept is straightforward: when an anhydride is added to water, it typically regenerates the related acid.

• Example: Carbon dioxide (\( CO_2 \)) acts as an anhydride for carbonic acid. When combined with water, \( CO_2 \) forms \( H_2CO_3 \).
• For perchloric acid, \( Cl_2O_7 \) is the corresponding anhydride, as shown in the equation:
  \[ Cl_2O_7 + H_2O \rightarrow 2 HClO_4 \]

This regeneration makes anhydrides vital in practical and theoretical chemistry for understanding acid formation.